426 VARIETIES. 



We would refer all those interested in the subject to an essay upon the proper name of 

 the talcose schist of Vermont, under the heading of talcose schist among the azoic rocks. 



This common variety is found upon every section crossing the formation. It has ;i 

 peculiarly bright color in its westerly portions in Rutland County, also upon a small 

 range of this rock running from Fairhavcn to Sudbury. 



Perhaps the most common variety of the talcoid schist is what we have denominated 

 talco-argillaceous schist. It is composed of a mixture of the common talcoid and argil- 

 laceous materials, sometimes the one, and again the other predominating. Often carbon- 

 aceous matter is present ; so much so as to blacken the hand by contact with it. In the 

 Cabinet there are specimens of this variety from Pownal, both from the small deposit of 

 this rock interstratified with the Eolian limestone, No. 8 ^, and from the principal range, 

 Nos. ^, 5. It is common upon Mt. Anthony, and in the west part of Bennington 

 and Arlington. Nos. j^, jfg, and r * s are of this variety, from the cap rock of Mt. Eolus. 

 No. r |g is from East Rupert. No. ^ from West Rutland, upon a spur of this rock pro- 

 jecting from the main belt, is plumbaginous. This variety does not seem to be confined 

 to any one part of the series. 



The third variety, talco-micaceous schist, is more common in this rock in Massachusetts 

 than in Vermont. It seems to be merely a further stage in the history of the rock, as it 

 has experienced a greater degree of metamorphism. This variety may be considered a 

 mixture of the three minerals, quartz, talckitc and mica. It may be either a mica schist 

 taking talckite into its composition, or a talcoid schist containing mica. Probably a large 

 part of the talcoid schist contains a small proportion of mica, or its constituents. Sec 

 No. ^ in the Cabinet, from Pownal. 



Occasionally there are talcoid grits associated with these schists. By talcoid grits we 

 mean a rock having the same color as the schists and the same general texture, but it has 

 a harsh feel, and is evidently mostly silicious in its composition. It passes into quartz 

 rock. Rarely this quartz rock is filled with numerous minute crystals of iron pyrites. 



These schists are filled in many places with irregular veins of quartz, not only hyaline, 

 but a fetid, porous quartz, from which some substance has been removed by decom- 

 position. The decomposing substances resemble chlorite. These veins are very common, 

 and resemble veins of hyaline quartz in the azoic talcose schists of Vermont, except 

 that the latter are not porous. 



There is a peculiar kind of conglomerate associated with the talcoid schists of Rutland 

 County. It consists of transparent quartz pebbles in a talcose paste. It is abundant in 

 Ira, Middletown, Wells, Poultney, and Pawlet. Upon Bird Mountain, in Ira, it consti- 

 tutes the mass of the rock. The pebbles are generally about the size of kernels of corn. 

 The rock on the summit is curiously mottled, and the conglomerate occurs in spots over 

 its surface. Its decomposition gives rise to a black powder, much like the peroxyd of 

 manganese. See Nos. g|g, gfg, jfg and ^- in the Cabinet. 



This conglomerate reminds us at once of the talcose conglomerates of Northern Ver- 

 mont, but not so much from its lithological appearance as its association with the so-called 

 talcose schists. We are not sure but that the advocates of the Taconic system would 

 regard the talcoid schists and the talcose conglomerates as belonging to the same belt 

 of rocks, though the continuity was destroyed by the erosion or depression of some parts 



